Blender ascii fbx adds a Armature bone before root bone UE4
Had this same problem and spent a day trying to work it out. Reverted back to Blender 2.74 and export with FBX 7.4 binary and it worked fine. 

For some reason Blender 2.75 and 2.76 add this bone, which means enabling root motion in Unreal Engine does nothing. This sucks because replacing a skeleton in Unreal when you have heaps of animations and montages is annoying. Really hope this gets fixed.